The present invention relates to circuits for validation of overhead bytes generally and, more particularly, to a method and an architecture for serial communication between an overhead generator and an overhead processor for such validation.
Referring to FIG. 1, a conventional circuit 10 is shown comprising an overhead processor 12, an overhead generator 14 and an overhead interface 16. The overhead processor 12 may receive or generate a number of signals TOH (transport overhead), TOHEN (transmit overhead enable), TOHCLK (transmit overhead clock), TPOHFP (transmit path overhead frame pulse) and TTOHFP (transmit transport overhead frame pulse) for transferring overhead bytes from the overhead generator 14 to the overhead processor 12. Generally, the signal TOH is the data for transmit, the signal TOHCLK is the clock for the overhead interface 16, the signal TTOHFP is the start of the frame from the overhead processor 12, and the signal TPOHFP is the payload indicator from the overhead processor 12. The signal TOHEN is an indicator received from the path overhead generator 14 indicating whether the current path overhead bytes should be used or not.
FIG. 2 shows the waveform for communication typical of the approach described above with respect to FIG. 1. As seen in FIG. 2, when the signal TOHEN is asserted on the first bit of the incoming overhead byte (i.e., TOH1, TOHEN), the overhead processor 12 recognizes the signal TOHEN as indicating that a valid overhead byte is to be used as the frame of a SONET device. When the signal TOHEN pin is de-asserted (i.e., TOH2) during the first bit of the overhead byte, the overhead processor 12 recognizes the overhead byte as not valid and uses the default value stored inside the overhead processor 12.
As shown in the description above, this previous approach uses a separate pin to communicate the validation of the overhead byte.
The present invention concerns a method of validating data between a path generator and a path processor, comprising the steps of (A) transmitting validation data from said path generator to said path processor on a data path, (B) sequentially transmitting data on said data path, (C) determining if the transmitted data is valid in response to the validation data and (D) using the overhead data by the processor when the overhead data is validated by the validation data.
Another aspect of the present invention concerns a circuit for validating overhead bytes comprising a data pin and a processor. The data pin may be configured to sequentially transmit one or more validation bits and an overhead data. The processor may be configured to determine if the transmitted overhead data is valid with respect to a previously sequentially transmitted validation data.
The objects, features and advantages of the present invention include a method and architecture that may provide (i) in-band signaling to communicate validation of overhead bytes, (ii) in-band communication in a serial communication scheme, and/or (iii) in-band communication without implementing a separate pin for such validation.